The present invention generally relates to methods and apparatus for reproducing an information signal recorded on a rotary recording medium at a high speed, and more particularly to a method and apparatus for reproducing a video signal recorded on an optical disc at a high reproducing speed by moving a light beam for reproducing the video signal across a track formed on the disc along which the video signal is recorded one or a plurality of times consecutively one track pitch by one track pitch.
Conventionally, there is a recording and reproducing apparatus for reproducing a video signal and an audio signal, recorded along a spiral or concentric track on an optical disc such as a video disc, by scanning the track by means of a light beam. Generally, the track of a video disc (referred to hereinafter as a disc) is divided into two through six portions. Usually, one field of a video signal constituting one frame of picture is recorded on one such portion. Thus, two successive track portions on a disc correspond to odd and even fields of the video signal. At a boundary between these two adjacent track portions is formed a vertical blanking interval recording region in which a vertical synchronizing signal is recorded. No video signal is recorded in this vertical blanking interval recording region. In a normal reproducing mode, the disc is rotated in a predetermined direction and the light beam traces the track as it moves across the recording area of the disc for example from an inner periphery thereof toward an outer periphery.
In such a recording and reproducing apparatus, there are instances that a user wishes to reproduce the recorded video signal at a high reproducing speed. Generally, in order to obtain high speed reproducing, it is necessary to reproduce an odd field video signal and an even field video signal which are separated from each other by a predetermined number of fields alternatively and consecutively. The aforementioned predetermined number of fields separating the odd and even fields are determined by the desired reproducing speed. Thus, it is necessary to move or jump the light beam from a first track portion on the disc in which odd (even) field information is recorded to a second track portion in which even (odd) field information is recorded. The second track portion aforementioned is separated from the first track portion by a predetermined number of tracks toward the outer or inner periphery of the disc responsive to the desired reproducing speed and a desired reproducing direction.
It is known that the one track pitch jump of the light beam across the disc repeated consecutively by (n-1) times during one revolution of the disc in a forward high speed reproducing mode results in a picture which is reproduced n times faster than the reproducing speed of the normal reproducing mode. Further, it is also known that the one track pitch jump of the light beam across the disc repeated consecutively by (n+1) times during one rotation of the disc in a backward high speed reproducing mode produces a picture reproduced n times faster than the reproducing speed of the normal reproducing operation.
In the high speed reproducing mode, no video signal is reproduced during the jump. As a result, a noise having a period of one to ten odds of H (H is a horizontal scanning interval) is produced. This noise appears on the screen as a horizontal line or a band. It is desirable, therefore, that such a noise is eliminated from the screen as much as possible by choosing the timing of the jump such that the jump is made during the vertical blanking interval.
In cases where the desired reproducing speed is relatively low such as twice the normal reproducing speed, the number of times the light beam is required to move or jump is relatively small, so that it is easy to confine the band shaped noise or a noise band in the vertical blanking interval therefore excluding the noise from the screen. However, as the desired reproducing speed increases to a relatively high speed such as a speed which is ten times faster than the normal reproducing speed, it becomes increasingly difficult to confine all of the jumps of the light beam within the vertical blanking interval. This is mainly due to the limitation imposed by the inertia of an actuator which causes the jump of the light beam. Thus, the aforementioned noise band appears on the screen and the quality of the reproduced picture is reduced.
Further, there is a problem in the conventional reproducing apparatus whereby the position of a noise band appearing on the screen in one field of the picture and the position of a noise band appearing in the succeeding field are not always identical. As a result, the area of the screen occupied by the noise band increases resulting in further deterioration of picture quality.